WASHINGTON -- President Barack Obama is hailing a "historic day" for uninsured Americans who now can purchase health care coverage through new insurance exchanges.

He says the opportunity is life-changing for those who could not get access to health care before Tuesday's launch of the exchanges.

The president spoke in the White House Rose Garden Tuesday alongside a group of citizens who plan to purchase insurance through the system.

His message to Americans is that the health care exchanges will not shut down since they are previously funded. Much of federal government has been shuttered because Congress hasn't passed a budget bill.

Obama accused Republicans of making the concept of keeping people uninsured "the centerpiece of their agenda."